added Latch utility

2 files changed, 107 insertions, 0 deletions

diff --git a/vespalib/src/tests/latch/CMakeLists.txt b/vespalib/src/tests/latch/CMakeLists.txt
new file mode 100644
index 00000000000..57a67d74868
--- /dev/null
+++ b/vespalib/src/tests/latch/CMakeLists.txt
@@ -0,0 +1,8 @@
+# Copyright 2017 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+vespa_add_executable(vespalib_latch_test_app TEST
+    SOURCES
+    latch_test.cpp
+    DEPENDS
+    vespalib
+)
+vespa_add_test(NAME vespalib_latch_test_app COMMAND vespalib_latch_test_app)
diff --git a/vespalib/src/tests/latch/latch_test.cpp b/vespalib/src/tests/latch/latch_test.cpp
new file mode 100644
index 00000000000..f29b673e508
--- /dev/null
+++ b/vespalib/src/tests/latch/latch_test.cpp
@@ -0,0 +1,99 @@
+// Copyright 2018 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+
+#include <vespa/vespalib/testkit/test_kit.h>
+#include <vespa/vespalib/util/gate.h>
+#include <vespa/vespalib/util/latch.h>
+
+using namespace vespalib;
+
+TEST("require that write then read works") {
+    Latch<int> latch;
+    EXPECT_TRUE(!latch.has_value());
+    latch.write(42);
+    EXPECT_TRUE(latch.has_value());
+    EXPECT_EQUAL(latch.read(), 42);
+    EXPECT_TRUE(!latch.has_value());
+}
+
+TEST_MT_FFF("require that read waits for write", 2, Latch<int>(), Gate(), TimeBomb(60)) {
+    if (thread_id == 0) {
+        EXPECT_TRUE(!f2.await(10));
+        f1.write(123);
+        EXPECT_TRUE(f2.await(60000));        
+    } else {
+        EXPECT_EQUAL(f1.read(), 123);
+        f2.countDown();
+    }
+}
+
+TEST_MT_FFF("require that write waits for read", 2, Latch<int>(), Gate(), TimeBomb(60)) {
+    if (thread_id == 0) {
+        f1.write(123);
+        f1.write(456);
+        f2.countDown();
+    } else {
+        EXPECT_TRUE(!f2.await(10));
+        EXPECT_EQUAL(f1.read(), 123);
+        EXPECT_TRUE(f2.await(60000));        
+        EXPECT_EQUAL(f1.read(), 456);
+    }
+}
+
+struct MyInt {
+    int value;
+    MyInt(int value_in) : value(value_in) {}
+    MyInt(MyInt &&rhs) = default;
+    MyInt(const MyInt &rhs) = delete;
+    MyInt &operator=(const MyInt &rhs) = delete;
+    MyInt &operator=(MyInt &&rhs) = delete;
+};
+
+TEST("require that un-assignable non-default-constructable move-only objects can be used") {
+    Latch<MyInt> latch;
+    latch.write(MyInt(1337));
+    EXPECT_EQUAL(latch.read().value, 1337);
+}
+
+struct MyObj {
+    static int total;
+    int *with_state;
+    MyObj(int &with_state_in) : with_state(&with_state_in) {}
+    MyObj(MyObj &&rhs) {
+        with_state = rhs.with_state;
+        rhs.with_state = nullptr;
+    }
+    void detach() { with_state = nullptr; }
+    ~MyObj() {
+        ++total;
+        if (with_state) {
+            ++(*with_state);
+        }
+    }
+    MyObj(const MyObj &rhs) = delete;
+    MyObj &operator=(const MyObj &rhs) = delete;
+    MyObj &operator=(MyObj &&rhs) = delete;
+};
+int MyObj::total = 0;
+
+TEST("require that latched objects are appropriately destructed") {
+    int with_state = 0;
+    int total_sample = 0;
+    {
+        Latch<MyObj> latch1;
+        Latch<MyObj> latch2;
+        Latch<MyObj> latch3;
+        latch2.write(MyObj(with_state));
+        latch3.write(MyObj(with_state));
+        latch2.read().detach();
+        EXPECT_TRUE(!latch1.has_value());
+        EXPECT_TRUE(!latch2.has_value());
+        EXPECT_TRUE(latch3.has_value());
+        EXPECT_EQUAL(with_state, 0);
+        EXPECT_GREATER_EQUAL(MyObj::total, 1);
+        total_sample = MyObj::total;
+    }
+    EXPECT_EQUAL(MyObj::total, total_sample + 1);
+    EXPECT_EQUAL(with_state, 1);
+}
+
+TEST_MAIN() { TEST_RUN_ALL(); }